Multiconductor cable



Feb. 14, 1939. M HOCHSTADTER 2f47095 MULT ICONDUCTOR CABLE Filed Aug.25, 1935 Patented Feb. 14, 1939 ,UNITED STATES PATENT OFFICEMULTICONDUCTOR CABLE Martin Hochstadter, Brussels, Belgium ApplicationAugust 23, 1935, Serial No. 37,571 In Great Britain January 17, 1935' 4Claims.

Such cables are known in the art under thel name of SL-type Ycables andup to the present they have been made from singles with a circularcross-section.

Recently, however, it has become desirable for severalelectricalvengineering purposes, to make ythe cross-section of each single of vsuchcables, non-circular, for instance, sector shaped or oval.

Now, while the stranding of circular shaped singles to a multi-corecable oiers no particular dimculty, the stranding of such cablescomposed of non-circular singles is more difficult.

The drawbacks of such a cable consist mainly in the difficulties whicharise from the necessary twisting of each single round its axis duringthe stranding and from the damage which is thereby done to theinsulation and still more to the sheath and the binding or armor appliedupon the same. l

If the sheath and the armoring, or binding tapes round the same, of suchan oval single are twisted during the stranding together of the singlecables, then any imperfections or impurities existing in the lead, orother material composing the sheath, are liable to result in damage tothe sheath. At the same time the binding or armoring will be loosenedfrom the sheath and thereby lose its desired effect or will be broken orpressed into the lead according to the direction of the twistingrelatively to that of the taping.

The object of this invention is to avoid such damage tothe sheath andbinding or armoring 40 of each single core cable by avoiding thetwisting of the sheathed cables about their own respective axes.

Other objects and advantages will become apparent to those skilled inthe art from the following description of a preferred practicalembodiment of the invention. It is to be understood that the inventionmay assume other forms according to the extent to which the variousadvantages are desired, and as determined by the particular class ofservice to which the cable is to be put, the availability of materialsof various kinds and other similar factors, without in any way departingfrom the scope of the invention as defined in the appended claims. Theinvention is based on the discovery that it is possible and advantageousto apply the sheath and also the binding or armor, if any, to apretwisted insulated conductor.

Referring to the accompanying drawing illustrating a preferred mode ofcarrying the invention into eiTect:

Figure l` is a perspective view, partly broken away, of a section of thecable, and

Figure 2 is a similar view, illustrating only one of the single-corecables, prior to the assembly into a multi-core cable.

The three conductors I of the three-core cable shown in Figure 1 areeach constructed of a number of metallic-wires or strands whichvarehelically twisted, it being, however, understood that they 15 may alsoconsist of one solid wire. The twisting of this strand, or solid wire,is effected according to one of the methods well-known in the art. Bythis pre-twisting, the conductor, shown here as being of ovalcross-section, is provided with a 2l helical pitch, which is socalculated with reference to the pitch of assembly of the three cablesthat the conductor, when insulated and sheathed, will be of suchconfiguration and shape that it will automatically take its place in theassembly 25 without further twisting round its own axis. Each suchpre-twisted conductor I is then provided with paper taping or otherinsulation 2, and if desired with 'an electric shield, in the form of asurface metallization, a tape of metal, conducting 30 paper orotherwise, such shield or tape being perforated or not, and wound withoverlap or with intervals between turns.

Such pre-twisted conductors and their manufacture are known per se inthe art. It is also 35 well known how to strand such pre-twistedinsulated conductors together to a multi-core cable, which is thenimpregnated and finally provided with a leadsheath and armor.

According to thisinvention, however, the pre- 40 `twisted insulatedconductors are provided with a lead sheath 3 each separately, before aplurality of these lead-sheathed twisted conductors, i. e. pre-twistedsingles are stranded together to a multi-core SL-type cable. 45

It has been found that the passing of the pretwisted insulatedconductors through the lead press or other machine to cover them with aWater-tight sheathing can be carried out, in spite of the particularcorkscrew-like shape of these 50 conductors. Up to a certain amount ofdeviation of the oval or sector shape from the circular form, it is evenpossible to use a circular shaped die-box, without rotating the same orthe conductor. It is only necessary to arrange the die .2S

` have, when assembled in the cable according to Figure l.

In assembling, all the known arrangements and precautions may be used tovary the speed of the machine, to suitably shift the angular position ofthe individual single-core drums and otherwise, in order to adapt thepitch of the stranding to the pitch of the single-cores. During theassembly, the'spaces 4 may be provided with fillers of insulatingmaterial or they may be left free, or distance pieces, in the form ofwire spirals, tubes, etc., may be inserted therein.

The three singles as assembled, are held together in any well knownmanner, for instance, by bindings or wrappings of textile material,metal tapes or wires. A sheath of lead or other material may also beapplied to enclose the stranded separately lead-sheathed cores and onthis outer sheath any known protection, bedding and armoring may beemployed. In Figure 1, a metal tape 5 of steel or other suitablematerial is shown to be wound round the assembled conductors.

The outer protecting sheath or armor may be circular or non-circular,the latter form being shown in Figure 1.

In Figure l, the cores are shown to be stranded together, with the leadsheaths 3 touching each other. But, of course, any known wrapping orother protection, without or combined with a reinforcing armor in theform of a metal tape or otherwise may be applied on these separatelylead-sheathed cores, before they are stranded t0- gether.

The metallization of the surface of the insulated cores is not shown inFigures 1 and 2, as it is not essential for the invention, and it may beapplied or not before the lead sheathing of the cores, according to theparticular purpose.

It is to be understood that the invention is no-t limited to pluralitiesof single conductors of the in different known manners; for instanceQbymeans of eccentric insulating layers or spacings, by a crushing of acircular shaped insulation to make it oval, by a non-uniform thicknessof the lead, or otherwise.

If the insulation of the single core cables is to be impregnated, thematerial and the manner of carrying out such impregnation is immaterialwith regard to this invention; the impregnating process may take placein any of the well known manners before or after lead sheathing, afterthe assembly or even after the laying of the cable.

What I claim is:

1. The method of manufacturing multipleconductor cables with separatelyinsulated and sheathed conductors laid up in helical form,

which comprises preshaping each individual conductor to a helical formand in a configuration suitable for the helical assembly of the severalconductors, applying insulation in a non-circular form to eachindividual conductor, applying a continuous water-tight extrudedmetallic sheathing to the individual preshaped non-circular insulatedconductors, assembling the sheathed conductors helically in accordancewith the preL shaped configuration thereof to form a cable substantiallydevoid of internal torsional stresses.

2 1. A multiple-conductor cable comprising a plurality of insulatedsingle conductors -of noncircular form, each insulated conductor beingpretwisted to helical form so that the plurality of conductors may belaid together helically around the cable axis, and a continuous extrudedmetal sheath applied to each pretwisted insulated conductor, theindividual sheathed conductorsbeing free of torsional twist on theirindividual axes.

3. A multiple-conductor cable comprising a plurality of insulated singleconductors, each conductor being pretwisted to helical form so that theplurality of conductors may be laid together helically around the cableaxes, and a continuous extruded metal sheath of non-circular formapplied to each pretwisted insulated conductor, the individualsheathedconductors being free of torsional twist on their individual axes.

4. A multiple-conductor cable comprising a plurality of insulated singleconductors, each conductor being pretwisted to helical form so that theplurality of conductors may be laid together helically around the cableaxis, and a continuous extruded metal sheath of non-circular formapplied to each pretwisted insulated conductor, the individual sheathedconductors being free of torsional twist on their individual axes, and ametal protective covering for said sheathed conductor.

MARTIN HOCHSTADTER.

